This invention relates to an improved tube feeler for an instrument which measures the position of various points of interest in a three-dimensional space and, more particularly, to a tube feeler which accommodates many different ranges of tube sizes.
The copending application describes an instrument for measuring the position of points along a straight portion of a preformed rod, tube or pipe hereinafter referred to as a tube. The measurements may be converted to vectors representing the straight portions and used to generate instructions to a bending machine for manufacturing a reproduction of the tube. A column is attached to a carrier which moves along one edge of a work table on which the tube is supported. The column has an upper end at which a first arm is provided for movement in a vertical plane. A second arm, having a carrier mounted at its end, is pivoted with respect to the first arm for further movement in the vertical plane. The carrier swivels about the axis of the second arm and has an offset end portion on which a tube feeler is mounted. The tube feeler has surfaces for engaging the preformed tube and is a single outwardly opening U-shaped member which accommodates a wide range of tube diameters. When the tube is engaged by the tube feeler, projections of the axis of the second arm and the axis of the tube feeler intersect at the centerline of the tube. Resolvers provide signals indicating the location of the carriage and the angles of the two arms, collectively defining the position of the intersection of the axis projections. The tube feeler, however, must be removed and replaced with a tube feeler of another size to accommodate various ranges of tube diameters.
I have developed an improved tube feeler which may be mounted on the offset end portion of an apparatus for measuring points along the straight portions of a preformed tube. The improved tube feeler is capable of accommodating various ranges of tube diameters. The improved tube feeler could also be used with other types of apparatus such as that disclosed by Eaton U.S. Pat. No. 3,944,798 or McMurtry British Pat. No. 1,329,708.